1. Field of the Invention
The present invention relates to a liquid crystal compound having at least two acryloyloxy groups on a side chain thereof, a composition containing the compound, a polymer obtained from the compound, and use thereof.
2. Description of the Related Art
In recent years, a liquid crystal compound having polymerizability is utilized as a polymer having optical anisotropy for a polarizing plate, a retardation plate and the like. This is because the compound has optical anisotropy in a liquid crystal state, and the orientation of molecules in the liquid crystal is fixed through polymerization. Optical characteristics that are required for the polymer having optical anisotropy vary depending on targets, and it is important to provide such a compound that has characteristics adapted to purpose. The compound is generally used after converted to a polymer and then molded. In the compound used in this manner, characteristics of a polymer thereof, in addition to the optical anisotropy, are important. The characteristics include a polymerization rate, and transparency, mechanical strength, coating property, solubility, a degree of crystallinity, contraction property, water permeability, water absorbency, a melting point, a glass transition point, a clearing point and chemical resistance of the polymer.
Various kinds of liquid crystal compounds having polymerizability have been known (for example, in JP-A-7-17910, JP-A-8-3111 and JP-A-9-316032). However, the conventional compounds have room for improvement in such characteristics as liquid crystallinity, compatibility with another compound and optical anisotropy. Furthermore, polymers thereof may not always have appropriate heat resistance, mechanical strength and chemical resistance. Accordingly, there have been demands of development of such a compound that is excellent in various properties including a high maximum temperature of the liquid crystal phase, a low minimum temperature of the liquid crystal phase, a wide temperature range of the liquid crystal phase and excellent compatibility, and such a polymer that is obtained by using the compound and is excellent in various properties including heat resistance, mechanical strength and chemical resistance.
A first object of the invention is to provide a polymerizable liquid crystal compound that has necessary characteristics, such as optical anisotropy, and a polymerizable liquid crystal composition that contains the compound. A second object of the invention is to provide a polymer that is excellent in plural characteristics including heat resistance, mechanical strength and chemical resistance, and a molded article having optical anisotropy that is obtained by using the polymer. A third object of the invention is use of the polymer utilizing the characteristics thereof. A fourth object of the invention is to provide a liquid crystal display device containing the polymer. The aforementioned and other objects of the invention will be apparent from the following description.